Field
Implementations of the present disclosure generally relate to the fabrication of integrated circuits. More particularly, the implementations described herein provide techniques for deposition of boron-carbon films on a substrate.
Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip designs continually calls for faster circuitry and greater circuit density. The demands for faster circuits with greater circuit densities impose corresponding demands on the materials used to fabricate such integrated circuits. In particular, as the dimensions of integrated circuit components are reduced to the nanometer scale, it is now necessary to use low resistivity conductive materials as well as low dielectric constant insulating materials to obtain suitable electrical performance from such components.
The demands for greater integrated circuit densities also impose demands on the process sequences used in the manufacture of integrated circuit components. For example, in process sequences that use conventional photolithographic techniques, a layer of energy sensitive resist is formed over a stack of material layers disposed on a substrate. The energy sensitive resist layer is exposed to an image of a pattern to form a photoresist mask. Thereafter, the mask pattern is transferred to one or more of the material layers of the stack using an etch process. The chemical etchant used in the etch process is selected to have a greater etch selectivity for the material layers of the stack than for the mask of energy sensitive resist. That is, the chemical etchant etches the one or more layers of the material stack at a rate much faster than the energy sensitive resist. The etch selectivity to the one or more material layers of the stack over the resist prevents the energy sensitive resist from being consumed prior to completion of the pattern transfer.
As the pattern dimensions are reduced, the thickness of the energy sensitive resist must correspondingly be reduced in order to control pattern resolution. Such thin resist layers can be insufficient to mask underlying material layers during the pattern transfer step due to attack by the chemical etchant. An intermediate layer, called a hardmask, is often used between the energy sensitive resist layer and the underlying material layers to facilitate pattern transfer because of its greater resistance to the chemical etchant. It is desirable to have thin hardmasks that have both high etch selectivity and are easy to remove after the etching process is complete. As critical dimensions (CD) decrease, current hardmask materials lack the desired etch selectivity relative to underlying materials and are often difficult to remove.
Boron-carbon films have good mechanical properties, excellent step coverage, good wet etch resistance and a high dry etch selectivity for low dielectric films. All of these characteristics are beneficial for applications such as lithographic hard masks to low-k dielectric etching and self-aligned double-patterning processes. However, due to their amorphous nature, amorphous boron films tend to have a high film stress, which causes line bending damaging the integrated circuit. Amorphous carbon films have poor etch selectivity, which necessitates thick hardmasks. Thick hardmasks are not suitable due to decreased transparency, and pattern bending or collapse at higher aspect ratios.
Therefore there is a need for a transparent hardmask film with improved etch selectivity. There is also a need for methods for depositing improved hardmask layers.